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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38232ec369fsm11374271f8f.70.2024.11.19.07.15.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Nov 2024 07:15:44 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 19 Nov 2024 16:15:42 +0100 To: Peter Zijlstra Cc: Andrii Nakryiko , Jiri Olsa , Oleg Nesterov , Andrii Nakryiko , bpf@vger.kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Masami Hiramatsu , Alan Maguire , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [RFC perf/core 05/11] uprobes: Add mapping for optimized uprobe trampolines Message-ID: References: <20241105133405.2703607-1-jolsa@kernel.org> <20241105133405.2703607-6-jolsa@kernel.org> <20241105142327.GF10375@noisy.programming.kicks-ass.net> <20241119091348.GE11903@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241119091348.GE11903@noisy.programming.kicks-ass.net> On Tue, Nov 19, 2024 at 10:13:48AM +0100, Peter Zijlstra wrote: > On Mon, Nov 18, 2024 at 10:06:51PM -0800, Andrii Nakryiko wrote: > > > > > Jiri, we could also have an option to support 64-bit call, right? We'd > > > > need nop9 for that, but it's an option as well to future-proofing this > > > > approach, no? > > > > > > hm, I don't think there's call with relative 64bit offset > > > > why do you need a relative, when you have 64 bits? ;) there is a call > > to absolute address, no? > > No, there is not :/ You get to use an indirect call, which means > multiple instructions and all the speculation joy. > > IFF USDT thingies have AX clobbered (I couldn't find in a hurry) then > patching the multi instruction thing is relatively straight forward, if > they don't, its going to be a pain. I don't follow, what's the reason for that? jirka